The RAM-108U consists of a double socket arm, 2.5" diameter round base that contains the universal AMPs hole pattern and single strap base. The strap will accommodate rails from 1" to 2.1" in diameter. The trolling motor stabilizer will take every bit of the vibration out of your trolling motor while all the time protecting the head, shaft and mount from damage. A must for any angler with a bow mount trolling motor. The maximum allowable distance between the mounting surface on the boat and the lowest point of the trolling motor shaft is 8.75". Distances shorter than this are compatible.